Starting jet formation through eversion of elastic sheets

Abstract

Starting jet is observed in many biological systems as in the human heart and the propulsion of aquatic creatures, which are composed of deformable structures that interact with the fluid. These structures can be modeled as flexible sheets for understanding complex biological systems and used for effective fluid transport. In this study, an everting sheet structure is devised to generate a fast jet with high impulse by taking advantages of an elastic sheet. The formation of a starting jet flow through eversion process is investigated experimentally by using a simplified model that represents an everted structure. The ends of two everted elastic sheets with a large aspect ratio are clamped at both sides of a rectangular channel, and the other ends of them are in contact with each other in the middle of the channel. The dynamics of the flexible sheets during the eversion process are examined to understand how the formation of a jet is changed by the interaction with the sheets with different lengths $L_s$ and bending rigidities $B$ of the sheets. From the obtained flow field by particle image velocimetry, a much faster jet with the improved hydrodynamic impulse is generated in the presence of elastic sheets. Such formation of a fast jet with high impulse is expected to suggest new approach for medical applications such as treating total occlusions in the blood vessel or transdermal drug delivery.